For many years it has been desired to make plastic materials from polymers such as polyvinyl chloride (PVC), polyvinyl acetate (PVAc), and olefin polymers (EPDM) which are either biodegradable by microorganisms or environmentally degradable such as in a landfill. In spite of considerable efforts, landfills are becoming inundated with plastic materials, and articles made therefrom, that will not degrade perhaps for centuries. This is especially true for vinyl halide and olefin polymer materials such as PVC and EPDM that are considered non-biodegradable, that is, they persist in landfills under anaerobic conditions indefinitely without noticeable decomposition. This factor limits the acceptance of PVC and polyolefins in many products where their useful balance of properties and low cost would be attractive. An example is that of printable film and sheet. If a sample of EPDM or flexible (plasticized) PVC is tested per ASTM D 5526, Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated Landfill Conditions, there is no appreciable weight loss or change in appearance after 100 days at 97° F. in contact with simulated household waste. In contrast, cellulosic polymers and other biodegradable plastics, such as polylactic acid and polycaprolactone, are completely consumed.
There has been a particular need for a compostable polymer composition for use in many end products such as polyvinyl chloride, polyvinyl acetate or olefin polymer films, banners, billboards, signs, laminates, ink jet media, diapers, hygienic pads and the like. These products must satisfy properties for practical purposes such as tear strength, tensile and impact strengths to function in many useful articles. However, the same properties that make them useful lead to their lack of biodegradability. PVC, PVAc and olefin polymers have achieved widespread usage. However, the explosive growth of such thermoplastics or elastomers has aggravated the problem of disposing of them, and has caused their accumulation in landfills. Very little of these polymeric waste products degrade in most landfills because of anaerobic conditions. The problem has become aggravated because of the shortage of landfills and municipalities are seeking to restrict the use of plastics because of their inability to degrade in landfills.
Environmental concerns with existing polymer stabilizers have stimulated interest in alternative stabilizers including organic based stabilizers. For example, in the pipe industry, PVC has long been stabilized with heavy metals, such as lead and cadmium. However, in Europe, replacement of lead-based stabilizers is currently one of the main focuses. As part of the voluntary initiative of Vinyl 2010, the European Vinyl Industry is committed to replace lead stabilizers in all PVC applications by 2015. Thus, there has been considerable interest in developing a new generation of environmentally acceptable heavy metal-free PVC stabilizers that prevent degradation and change in color during processing, and also provide tangible benefits to the manufacturer of useful articles.
In addition to providing useful PVC plastic articles which are free of heavy metal stabilizers, it would be highly desirable to also make them compostable. Thus, plastic articles that are capable of withstanding environmental conditions could be made and their degradation by sunlight, moisture, temperature, and the like prevented during their service life. Plastic products for practical purposes must satisfy such properties as water impermeability and sufficient mechanical properties, such as tear, tensile and impact strengths to function in useful articles. For example, there is a particular need for indoor or outdoor signs, billboards, banners, images, protective barriers, backdrops, and building wall coverings to provide plastic sheet material which will withstand outdoor environmental conditions. In the case of disposable health care products, diapers, underpants, hygienic pads, and the like, these products must also satisfy such properties as water impermeability in order to prevent seepage of urine or other human waste products therethrough. Further, for health care and waste management, there are needs for disposable plastic products such as medical tubing, bags and utensils that are biodegradable.